'Star Wars' has an amazing new droid: How does the BB-8 work in real life?

Star Wars obsession is a totally natural and not at all life-threatening condition, but it will make you fixate on minutiae. For die-hard fans, Thursday was a day full of Star Wars minutiae to mull over. In addition to an action-packed second teaser trailer, we got a live glimpse of the rolling BB-8 droid in action.

For both Star Wars fans and robot fanatics, this was a revelation. The super-fast rolling robot had only been glimpsed in the first trailer, which was released late last year. But before a jam-packed, enthusiastic crowd at the Star Wars Celebration convention in Anaheim, California, a real BB-8 rolled out in front of Star Wars: Episode VII director J.J. Abrams and producer Kathleen Kennedy.

It has a robotic ball for a body, topped with an equally robotic head that not only doesn't fall off but also lets the body move freely below it.

As the stunned crowd looked on, Abrams explained the thinking behind the robot. "There were a lot of discussions about how having a CGI BB-8 would be so much easier for shooting," he said. "But we also knew it would be so much better for the film, for the actors, for the set, for the look of it, if it were performed. Neil Scanlan and his unbelievable team ... built and puppeteered BB-8 in the movie and did an extraordinary job, and it was better for the actors and it was better for the film itself."

As he spoke, BB-8 looked about and rolled back and forth across the stage, at one point circling around the R2-D2 droid that had rolled out moments earlier. There were no strings, but we knew it was some kind of remote-controlled robot, and something very special.

Kennedy said Disney Chairman Bob Iger "found the company that helped us discover the technology of what you're seeing right now. Because we now have BB-8 operating on its own, thanks to Bob."

So how does BB-8 work?

We can guess at half of it. The ball is obviously a giant remote-control robot puppet very much like one called Sphero. Sphero, from Orbotix, is a self-contained robot ball that communicates with a smartphone app via Bluetooth. You can run it in any direction using the in-app virtual joystick. It's incredibly responsive. Even without a camera in it to see where you're going, you can use line-of-sight and information from the robot about which way it thinks is forward and back to guide it precisely. Watch a video of Sphero in action and it may remind you a little bit of BB-8.

But what about the head?

BB-8's dome-shaped cap is clearly not attached — otherwise there's no way the robot ball could move freely. But it is holding on somehow. The leading theory is magnets; they could be used to allow the cap to float a millimeter or so off the surface of BB-8's main ball. However, that would not account for how it would stay on top of the moving ball.

Here's my best guess. The cap is a second robot; it, too, is remote controlled — that's how the head "looks" around — but its main job is to stay on top of the ball. So inside the cap you might find a gyroscope, which tells the robot which way is up. It may also have an accelerometer to detect motion. Underneath it wouldn't have magnetic levitation technology, but rather a set of magnetic wheels that roll rapidly to keep it in place. It knows which way to roll based on the sensor info.

"That could be the case, but it could also use the wheels to accelerate in a given direction,” said Ralph Hollis, a research professor in the Carnegie Mellon Robotics Institute and the father of the Ballbot.

A ballbot uses a regular ball — and a lot of robotic technology to balance on top of the ball, and even move the entire robot by rolling the ball underneath. Hollis thinks my theory is possible, but told me it's also just as likely that the wheels in BB-8's head are, in fact, driving the entire robot, so BB-8's big ball is the dumb ball underneath.

The technology might work something like the robots in this IEEE Spectrum video.

"But I believe the BB-8 is more than just that," Hollis added. He agrees that inside BB-8's large ball is probably another robot system that rights itself as the BB-8 head moves about.

This is naturally all guesswork, and Hollis reminded me that we could both be wrong. But somehow, I think these are the droids we've been looking for.

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